Seriously, the leader of Germany in the 1930's, Stalin, Putin, Saddam Hussein, now Xi. All seized power domestically and then couldn't help themselves when it came to neighboring countries.
I’m not trying to make point about Stalin. Just trying to find if this is really a rule, but my historical knowledge is pretty limited. Intuitively I feel any overpowered political entity end up like shit. But interesting to see real data.
Stalin did start many wars, disastrous invasion of Finland, invasion of Poland, Molotov-Ribentrop pact with Germany and so on.
Also I forgot to add Mussolini and his designs on Greece, Balkans, North and the Horn of Africa.
You’d need to generalize the pop science to the British, French, Spanish and portugues empires then address the genocide of indigenous tribes by America, Canada and Australia